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Mars CubeSat Telecom Relay Constellation_JPL Final
The document proposes a 4-CubeSat constellation in Mars orbit to augment telecommunications relay capabilities for surface assets. The CubeSats would be deployed from a 2022 Mars Telecom Orbiter into a 350 km circular orbit with 70 degree inclination. Each 6U CubeSat would carry an IRIS transponder, Ka-band reflectarray antenna, and UHF antennas to provide direct-to/from-Earth relay and cross-link relay with orbiters. Analysis showed the design could meet power and propulsion requirements to operate for two Mars years.
Mars CubeSat Telecom Relay Constellation_JPL Final
- 1. Mars Telecommunications CubeSat ConstellationRelay December 10, 2015 PI: Dr. David Spencer Students: Rohan Deshmukh Swapnil Pujari Giovanny Guecha
- 2. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work MarsTelecom Investigation Team David Spencer, Aerospace Engineering Space systems, mission design Rohan Deshmukh, Aerospace Engineering Packaging, system engineering The Mars Telecom Investigation Team would like to acknowledge and thank the following people for their input and support during this study: JPL: Tom Komarek, Robert Lock, Chad Edwards, Ryan Woolley, Sara Spangelo, Courtney Duncan Georgia Tech: Glenn Lightsey, Adam Snow, Sean Chait, Terry Stevenson Swapnil Pujari, Aerospace Engineering, Telecommunications, data volumes Giovanny Guecha, Aerospace Engineering, Subsystem trade studies
- 3. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work ConceptOverview 3 • A constellation of four 6U CubeSats in high inclination Mars orbit augments telecom relay capability for landed assets – Benefits include increased frequency of command (forward link) opportunities, and increased return data volumes from surface assets – Constellation utilizes both DTE/DFE relay as well as UHF cross-link relay with existing telecommunication orbiters • Concept is targeted for 2022 launch opportunity, deployed from 2022 Mars Telecom Orbiter (MTO) – 4-CubeSat constellation established with 350 km circular altitude, 70 deg inclination orbit (or same inclination as MTO), phased to be evenly spaced around the orbit – Study team also evaluated constellation performance in an equatorial orbit • Two aerocapture delivery systems deployed during Mars approach capture into equatorial Mars orbit; each aerocapture system deploys two CubeSats into low- Mars orbit. • CubeSats deployed from launch vehicle upper stage at launch, use ion propulsion for interplanetary transfer and orbit capture. This approach was found to be infeasible with current CubeSat-class ion propulsion systems.
- 4. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work MarsMission Architecture 4 Credit: Jet Propulsion Laboratory Telecom CubeSat Constellation
- 5. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work KeyDriving Requirements • The telecommunications relay constellation shall consist of four 6U CubeSats. – 36 cm x 24 cm x 12 cm 6U form factor, maximum CubeSat mass 14 kg. • The CubeSats shall be deployed from MTO into low-Mars orbit, and shall maneuver into the constellation configuration. • The constellation orbit shall have a 350 km altitude, with an inclination equal to that of the 2022 Mars Telecom Orbiter (MTO). • The CubeSats shall be phased 90 deg apart along the orbit. • The constellation shall provide direct-from-Earth (DFE) forward link and direct-to-Earth (DTE) return link relay for near-equatorial surface assets. • The constellation shall provide UHF forward- and return-link relay between surface assets and MAVEN/TGO/MTO. • The CubeSats shall be capable of operating for two Mars years in the Mars environment. 5
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- 7. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work FlightSystem Deployed Configuration 7 Front Isometric View Back Isometric View
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- 9. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work Telecommunications Subsystem ComponentName Quantity Telecom IRIS Transponder v2 1 K/Ka-Band Reflectarray 1 UHF 4 Monopole Antenna (ISIS) 1 IRIS Transponder v2 (NASA JPL): – Currently: X-Band (Rx/Tx) – Capabilities: UHF, Ka (both Rx/Tx) – Max 5W RF Output Power – Radiation Tolerant – BPSK Modulation K/Ka-Band Reflectarray Antenna1 UHF 4-Way Monopole Antenna 9 Telecommunications Characteristics Value Patched Area 33 x 27 x 0.24 cm Antenna Gain 33.5 dBi Frequency2 32 GHz Stowed Area 30 x 10 x 0.72 cm 1. Antenna characteristics are based off existing ISARA Reflectarray Antenna 2. Frequency modified to meet DSN specifications/ IRIS v2 capabilities Sources: CubeSat Antenna Datasheet, NASA IRIS V2 CubeSat Deep Space Transponder, NASA
- 10. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work Structure PumpkinSupernova 6U aluminum structure provides mounting locations for all subsystem components o 6U CubeSat structure complies with CubeSat deployer standards - 12 cm x 24 cm x 36 cm - MPV Mass: 14 kg 35.7 cm 12.4 cm 23.9 cm Stowed CubeSat Configuration Pumpkin Supernova 6U aluminum structure MEV Mass: 12.2 kg 10 Subsystem Component Name Quantity Structure Pumpkin Supernova 6U 1 Aluminum Shielding1 5 1. Shielding assumed to be 1.5 mm thick and covers all structure sides except cold gas thruster
- 11. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work ElectricalPower Subsystem Subsystem Component Name Quantity EPS Clyde Space FLEX EPS 1 CS 30 Whr Battery 2 CS Deployable Double Sided 6U Panels 6 CS 6U Body Mounted Solar Panels 2 K/Ka-Band Reflectarray 1 Clyde Space FLEX EPS - 12 BCR inputs, enough for many solar panels - On board over/under charge protection - Placed in vault for radiation mitigation Clyde Space Batteries – 30 Whr batteries, sync with PDM board – Built in heaters Clyde Space Customized Solar Panels • 24 cells per face – 48 cells on one panel (double-sided) • Solar Cell Efficiency: 28.3% • Customization Required 11 K/Ka-Band Reflectarray (ISARA) • 24 cells integrated into reflectarray
- 12. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work AttitudeDetermination & Control 5/9/2016 12 Subsystem Component Name Quantity ADCS BCT-XACT Module 1 • Size: 0.5U • Pointing Accuracy: ±0.003° (2 axes) ±0.007° (3rd axis) • Low jitter 3-axis reaction wheel control • Desaturation with cold gas thruster • Customizable software Source: Blue Canyon Technologies
- 13. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work Propulsion SubsystemComponent Name Quantity Propulsion 2U Cold Gas Thruster 1 13 Cold Gas Thruster CAD Model1 Thruster Characteristics Value Dimensions (mm) 21x10x10 Dry Mass (kg) 1.5 Propellant Mass (kg) 0.92 Propellant R-236fa Power (W) 0.85 (nominal) 14** (startup) BOL Thrust* (mN) 40 Number of Nozzles 7 ΔV Capability (m/s) 31.5 Isp (s) 50 *per nozzle ** 2ms to open valve 1currently being developed by Georgia Tech Space Systems Design Laboratory Nozzles
- 14. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work 14 Command& Data Handling • Proton 200k-L (Space Micro) – Flight heritage on TACSAT-2 – 1 GHz processor – 512 Mbyte SDRAM – 1.5W power draw – UART and GPIO interfaces • Radiation Hardening – TID: 100krad (Si) – SEFI: 100% recoverable – SEL: > 63 LET – SEU: <1 per 1000 days in GEO • FSW Architecture – Redundant software modules – Memory scrubbing – SEL and SEU detection – Reprogrammable on orbit
- 15. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work MasterEquipment List Subsystem Component Name Quantity CBE Mass (g) Contingency MEV Mass (g) ADCS BCT-XACT Module 1 850 5% 893 Telecom IRIS v2 Transponder 1 1200 15% 1380 UHF Monopole Antenna (ISIS) 1 100 5% 105 Ka-Band Reflectarray 1 500 15% 575 Propulsion Cold Gas Thruster (dry) 1 1500 15% 1725 Structures 6U CubeSat Structure 1 1640 5% 1722 Aluminum Shielding 1 990 5% 1039 C&DH Proton 200k Lite Processor 1 200 5% 210 EPS Clyde Space FLEX EPS 1 173 5% 182 CS 30 W-hr Battery 2 260 5% 546 CS Deployable 6U Panels 6 290 15% 2001 CS 6U Body Mounted Solar Panels 2 290 15% 667 Thermal Heaters 2 10 10% 22 MLI 1 200 5% 210 MEV Dry Mass 11,276 Propellant Mass 920 MEV Wet Mass 12,196 Mass Margin 1,803 (15%) MPV Mass 14,00015
- 16. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work PropellantBudget 16 Maneuver DV (m/s) Propellant (g) Orbit Transfer 22 614 Orbit Phasing 0.5 14 Orbit Maintenance 2.5 68 RW Desaturation N/A 50 Reserves 6.5 222 Total 31.5 920 Assumptions • Orbit transfer from 400 x 400 km orbit (injection from MTO) to 350 x 350 km orbit • CubeSats phased 90 deg apart in orbit • Orbit trim maneuvers once/month • Reaction wheel desaturation allocation 50 g
- 17. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work PowerBudget Subsystem Component Name Contingency (%) Safe Mode Power Draw (mW) Maneuvering Power Draw (mW) UHF Rx/Tx Power Draw (mW) DTE/DFE Power Draw (mW) ADCS BCT-XACT Module 10% 202 2024 2024 2024 Telecom UHF Antenna 10% 220 0 2200 0 IRIS v2 Transponder 25% 1475 1475 14750 14750 Propulsion Cold Gas Thruster 25% 0 2706 0 0 C&DH Proton 200k Lite 10% 1375 1375 1375 1375 EPS CS FLEX EPS 10% 165 165 165 165 CS 30 Whr Battery 10% 110 110 110 110 Thermal Heaters 15% 1150 288 288 288 MEV Total (W) 4.70 8.14 20.91 18.71 On-board Average Power Generation (W) 33.42 17
- 18. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work OrbitTimeline & Data Return Strategy 18
- 19. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work Results: –13% Battery Margin above DoD (5.25 Ahr) – Clyde Space estimates 35000 cycle life potentially over 7 year lifetime0 5 10 15 20 25 30 35 40 0 1 2 3 4 5 6 7 8 0 0.2 0.4 0.6 0.8 1 BatteryCharge/Draw(W) BatteryCharge(Ahr) Orbits Battery Charge DoD Minimum Power Generation Power Draw Battery Charge Cycle DoD Analysis 19 Battery Specs (Clyde Space 30Whr): • Quantity: 2 • Capacity: 7.5 Ahr • Voltage: 8.2 V DC • Rated DoD: 30% = 5.25 Ahr (lab tested for 5000 cycles) Operation Mode Power Draw (W) Power Generation (W) Maneuvering 8.14 33.42 DTE/DFE 18.71 33.42 UHF Rx/Tx 20.91 33.42 / 0 Safe (Eclipse) 4.70 0 EclipseDaylight Daylight
- 20. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work ThermalControl 20 • 3-Node thermal model applied at Mars – Finite differencing used to model temperature change with time • Active thermal control provided by temp sensors and heaters – Single Mars Eclipse (42 min) during mission operation – 1 W Heaters applied when below - 0° C • Paint selection, MLI used to establish desired passive thermal characteristics • Large deployable solar panels must be thermally isolated (kA ~ 4J/K) 2 2 1 3 Parameter 1 2 3 Primary Material Aluminum GaAs Silicon Surface Area (m2) 0.266 0.912 0.178 Mass (kg) 8.67 2.00 0.59 Cp (J/kg*K) 897 350 700 Power (W) 33.42 0 0 Absorptivity 0.031 0.637 0.11 Emissivity 0.039 0.85 0.05 Thermal Conductivity (W/m*K) 167 52 148 Source: Thermal Design and Analysis of Spacecraft, AFRL Component Temperature Limit (°C) 0 - 40
- 21. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work ThermalControl – Orbit In A Life Analysis 21
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- 23. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work Assumptions •DTE downlink data volume calculations based on Earth-to- Mars range (1 AU) • Transmit DTE/DFE when not in eclipse – Transmit 1.23 hours per orbit • 8 hours DSN (34 m BWG) pass per sol, 3 times per week – Multiple Spacecraft Per Antenna (MSPA) capability – Up to four simultaneous downlinks • UHF crosslink to MAVEN/TGO/MTO based upon orbit geometries, data rates consistent with average range 23
- 24. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work CommunicationsOpportunities 24 • 4-CubeSat constellation provides 16 overflights per sol with respect to an equatorial surface asset – MTO offers four overflights per sol, MAVEN two per sol • For 70 deg inclination orbit, twice daily communications “blackout” periods of ~8.5 hours occur, due to constellation orbit geometry – Outside of blackout periods, CubeSat constellation and MTO provide near-continuous communication opportunities with equatorial surface assets
- 25. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work EquatorialSurface Asset Coverage Plot 25 Time (UTCG) 2 x Blackout Period (approx. 8.5 hours) MAVEN Coverage Period (approx. 3.5 hours) Coverage Period (approx. 3.5 hours) CubeSat 4 MTO CubeSat 3 CubeSat 2 CubeSat 1
- 26. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work 4-CubeSatConstellation Return Link Capability 26 CubeSat Constell. Inclination (deg) Surface Asset Latitude (deg N) CubeSat Constell. Avg # of Passes/Sol CubeSat Avg. Pass Duration (min) Surface to CubeSat Constell. Avg. Data Volume (Mb/Sol) CubeSat Constell. Avg. Data Volume Per Sol via MAVEN (Mb/Sol) CubeSat Constell. Avg. Data Volume Per Sol via TGO/MTO (Mb/Sol) CubeSat Constell. Avg. Data Volume Per Sol DTE (Mb/Sol) 70 0 14.3 13.0 543 94 1142 342 70 10 14.6 13.0 553 94 1142 342 70 20 15.5 13.1 584 94 1142 342 0 0 45.7 17.5 3647 64 298 342 0 10 45.7 16.1 2373 64 298 342 0 20 45.7 10.8 914 64 298 342 Surface Asset on Mars TGO/MTO MAVEN CubeSat Constellation Earth UHF Ka-Band
- 27. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work 27 TechnicalRisks 2 3, 5, 6 4 1 Consequence Likelihood 1 – Solar panel deployment 2 – Radiation tolerance 3 – DTE Pointing accuracy 4 – Propulsion system performance 5 – Ka-band reflect array deployment 6 – UHF antenna deployment
- 28. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work 28 CostEstimate • Cost for 4 CubeSat constellation: $18.5M – 2022 launch, 2 years mission operations once on-orbit at Mars – Launch costs, DSN costs not included – Includes 30% reserves Cost Element Cost (FY'16 $K) Project Management, System Engineering $540 Flight System (4 CubeSats) $12,560 Environmental Testing $300 Flight System Testbed $550 Mission Operations, Ground Data System $270 Total Mission Cost w/o Reserves, Excluding L/V $13,460 Reserves (30%) $4,280 Total Mission Cost $18,500
- 29. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work Conclusions •CubeSat constellation provides a dramatic increase in the frequency of communications opportunities with landed assets – Frequent uplink opportunities would be a major benefit to operations teams scheduling the building and transmission of command products • Max possible data return via CubeSat constellation exceeds the data volumes that may be returned directly through either MAVEN, TGO or MTO – Ex: Equatorial 4-CubeSat constellation can return > 300 Mb/sol DTE, compared with 177 Mb/sol for surface asset relay through MAVEN • Technical resource budgets show that 6U CubeSat design is feasible for Mars telecommunications relay application 29
- 30. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work NextSteps • Starting in January 2016, we would like to develop a FlatSat capability, including the CubeSat avionics – C&DH, EPS, Telecom, ADCS • Existing hardware-in-the-loop testing capability and SoftSim6D will be used to emulate hardware operability in Mars orbit – Begin flight software development – Define all interfaces between key subsystem components 30
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- 33. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work DTEReturn Link Budget 33 Parameter Value Frequency (GHz) 32 RF Output (W) 2 CubeSat Antenna Gain (dBi) 33.5 Path Length (km) 4E08 34 m DSN Receive Gain (dBi) 79.5 Noise Temperature (K) 31 Data Rate (kbps) 4.7 Eb/No (dB) 7 Required Eb/No (dB) 2 Link Margin (dB) 4 Parameter Value Frequency (GHz) 32 RF Output (W) 2 CubeSat Antenna Gain (dBi) 33.5 Path Length (km) 6E07 34 m DSN Receive Gain (dBi) 79.5 Noise Temperature (K) 31 Data Rate (kbps) 28 Eb/No (dB) 7 Required Eb/No (dB) 2 Link Margin (dB) 4 Worst Case: 1 AUBest Case: 0.41 AU
- 34. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work DFEForward Link Budget 34 Parameter Value Frequency (GHz) 32 RF Output (W) 800 34m DSN Gain (dBi) 79.5 Path Length (km) 4E08 CubeSat Receive Gain (dBi) 33.5 Noise Temperature (K) 80 Data Rate (kbps) 100 Eb/No (dB) 7 Required Eb/No (dB) 2 Link Margin (dB) 12.6 Parameter Value Frequency (GHz) 32 RF Output (W) 800 34m DSN Gain (dBi) 79.5 Path Length (km) 6E07 CubeSat Receive Gain (dBi) 33.5 Noise Temperature (K) 80 Data Rate (kbps) 100 Eb/No (dB) 7 Required Eb/No (dB) 2 Link Margin (dB) 20.3 Worst Case: 1 AUBest Case: 0.41 AU
- 35. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work UHFCrosslink Return Link Budget 35 Parameter Value Frequency (MHz) 435 RF Output (W) 1 Orbiter Antenna Gain (dBi) 3 Average Path Length (km) 5,286 CubeSat Receive Gain (dBi) 0 Noise Temperature (K) 500 Data Rate (kbps) 2.1 Eb/No (dB) 12.6 Required Eb/No (dB) 9.6 Link Margin (dB) 2 Parameter Value Frequency (MHz) 435 RF Output (W) 1 Orbiter Antenna Gain (dBi) 3 Average Path Length (km) 1,513 CubeSat Receive Gain (dBi) 0 Noise Temperature (K) 500 Data Rate (kbps) 25.7 Eb/No (dB) 12.6 Required Eb/No (dB) 9.6 Link Margin (dB) 2 MAVEN CubeSatTGO/M22 CubeSat
- 36. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work UHFCrosslink Forward Link Budget 36 Parameter Value Frequency (MHz) 435 RF Output (W) 0.5 CubeSat Antenna Gain (dBi) 0 Average Path Length (km) 5,286 Orbiter Receive Gain (dBi) 3 Noise Temperature (K) 500 Data Rate (kbps) 1.1 Eb/No (dB) 12.6 Required Eb/No (dB) 9.6 Link Margin (dB) 2 Parameter Value Frequency (MHz) 435 RF Output (W) 0.5 CubeSat Antenna Gain (dBi) 0 Average Path Length (km) 1,513 Orbiter Receive Gain (dBi) 3 Noise Temperature (K) 500 Data Rate (kbps) 12.9 Eb/No (dB) 12.6 Required Eb/No (dB) 9.6 Link Margin (dB) 2 CubeSat MAVENCubeSat TGO/M22
- 37. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work Surface-to-CubeSatReturn Link Budget 37 Parameter Value Frequency (MHz) 435 RF Output (W) 1 Electra Antenna Gain (dBi) 3 Path Length (km) 1108 CubeSat Receive Gain (dBi) 0 Noise Temperature (K) 500 Data Rate (kbps) 48.0 Eb/No (dB) 12.6 Required Eb/No (dB) 9.6 Link Margin (dB) 2 Parameter Value Frequency (MHz) 435 RF Output (W) 1 Electra Antenna Gain (dBi) 3 Path Length (km) 1101 CubeSat Receive Gain (dBi) 0 Noise Temperature (K) 500 Data Rate (kbps) 48.6 Eb/No (dB) 12.6 Required Eb/No (dB) 9.6 Link Margin (dB) 2 Worst Case: 20° Surface AssetBest Case: 0° Surface Asset
- 38. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work CubeSat-to-SurfaceForward Link Budget 38 Parameter Value Frequency (MHz) 435 RF Output (W) 0.5 CubeSat Antenna Gain (dBi) 0 Average Path Length (km) 1108 Surface Receive Gain (dBi) 3 Noise Temperature (K) 255 Data Rate (kbps) 47.0 Eb/No (dB) 12.6 Required Eb/No (dB) 9.6 Link Margin (dB) 2 Parameter Value Frequency (MHz) 435 RF Output (W) 0.5 CubeSat Antenna Gain (dBi) 0 Average Path Length (km) 1101 Surface Receive Gain (dBi) 3 Noise Temperature (K) 255 Data Rate (kbps) 47.6 Eb/No (dB) 12.6 Required Eb/No (dB) 9.6 Link Margin (dB) 2 Worst Case: 20° Surface AssetBest Case: 0° Surface Asset
- 39. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work FlightSystem Deployed Configuration (KaPDA Version) 39 Front Isometric View Back Isometric View Stowed Isometric View 35.7 cm 22.2 cm 12.4 cm
- 40. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work RadiationMitigation • The Mars CubeSat design will advance the CubeSat standard for radiation tolerance to enable a two Mars-year baseline mission • Approaches to radiation mitigation: – Shielding – Radiation hardened electronics – Selected hardware redundancy – Software redundancy – Memory scrubbing – Fault tolerance by design 40 Source: Cressler, Radiation effects in SiGe Technology Image Credit: Xilinx
- 41. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work MarsAerocapture Concept 41 Mars Program Formulation Office National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Overview of Mission Events Entry (150 km) E+7min M2020 Site, E+4min E+9min P1 (Orbit #2) P0 E+3min Deploy Drag Skirt E-71 hrs Eject Aerocube on Divert Vector E-72 hrs Entry-73 Entry Enable Aerocube Controller Initialize IMU, Temp Sensors Record Telemetry -72 -71 -70 Eject Aerocube, Beacon Tones Deploy Aero-skirt Hibernate Wake from Hibernation Acquire Attitude Knowledge Warm Cat-bed Heaters Transmit Beacon Tones Turn to Entry Attitude Aeropass Jettison Aeroshell Earth Occultation Sun Eclipse Deploy Solar Arrays Periapsis Raise Maneuver (PRM) -2 -1 +1 +2 +3 +4 +5 +6 +7 +8 +9 +10 +11 +12 Periapsis #1 (P1) Start Orbit #2 MRO Visibility Aeropass 7min Eclipse 75min Earth Occultation 38min PRM E+6 hr Sun Earth MRO Divert-Deploy E-72 hrs Wake: Entry Attitude Transmit Beacon E-2 hrs tumbling Deploy HGA (in Orbit #2) Deploy Solar Arrays and UHF antennas 10/24/2013 6
- 42. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work EquatorialSurface Asset Coverage Plot: 0° Inclination Constellation 42 MAVEN CubeSat 4 MTO CubeSat 3 CubeSat 2 CubeSat 1 • Full coverage of equatorial surface assets – Maximum access gap time of 14 mins between different relays • CubeSat Relay averages 45 passes/Sol compared to MTO, 4 passes/Sol
- 43. Motivation/ Background Overview Flight System Technical Resource Budgets Summary Future Work MarsEphemeris Data Analysis 0.00 0.50 1.00 1.50 2.00 2.50 3.00 0 5 10 15 20 25 30 35 40 45 50 58500 59000 59500 60000 60500 61000 Mars-EarthDistance(AU) SMEPhaseAngle(deg) Modified Julian Date SME Phase Angle & Mars-Earth Distance from 2020-2025 SME phase Angle (deg) Mars-Earth Dist (AU) 5/9/2016 43 Max Earth-Mars Distance (AU) 2.64 Min Earth-Mars Distance (AU) 0.41 Max Phase Angle (°) 46.594
Editor's Notes
- #5 Final Consideration: Cubesats have very focused missions. Not enough space to accommodate communications. Develop infrastructure using off-the shelf components to provide lower costs while increasing performance.
- #7 MSL -> Ground asset MRO -> Comm Orbiter 2020 Rover -> Equitorial orbit 4 cubesats in constellation phased 90 deg apart Telecom -> cubesat 1,2
- #8 Here is a CAD model of the overall CubeSat in its deployed configuration with its respective front and back isometric views. The callouts represent the deployed system including the solar panel array, K/Ka-Band reflectarray, and UHF dipole antenna. The solar panel array, consisting of a total of 6 panels, deploys from the 3x2 U face shown where the existing body-mounted solar panel is. The reflectarray is stowed on the 1x3 U face and consists of 3 deployable panels. The UHF dipole antenna deploys on the bottom 1x3 U face through a spring-loaded mechanism.
- #9 Here is an exploded view of the cubesat’s s/c bus. All major subsystems are highlighted by respective callouts. With all subsystems accounted for in the CAD model, we have a volume margin of around 1.5U for further development. Note: deployable solar panel array not shown here.
- #10 Using the two aforementioned figure for current and future satellites around Mars, it can be seen that NASA is moving towards a standardization in Proximity operations around Mars through their Electra system and continuation of utilizing X-Band as their DS link. However, there is also a push to test K/Ka-Band communication links at Mars to satisfy the growing communication needs. Using these as driving factors, our proposal strives to not only meet current telecom needs, but improve on them by providing alternate cost-effective ways and test novel concepts in improving telecom performance. Two of these concepts can be seen in the IRIS Transponder v2 and K/Ka-Band reflectarray, which JPL has been pushing as the standard for telecommunication capabilities for interplanetary CubeSat/SmallSats. Notes for IRIS Transponder v2: X-Band Uplink Frequency Range: 7.145 – 7.190 GHz (compatibility verified in Version 1 and/or Version 2) X-Band Downlink Frequency Range: 8.4 – 8.45 GHz (compatibility verified in Version 1 and/or Version 2) Ka-Band: 32/34 GHz Deep Space, 26 GHz near Earth (capability under development) UHF Frequency Range: 390 – 450 MHZ (Receive supported on Version 2 but not yet verified, transmit capability under development) Notes for ISARA High Gain Antenna: HGA 0 Tx/Rx RHCP reflectarray at K/Ka-band 26 GHz comm antenna (100 MHz BW, min) Deployed on 3U P-POD bus / 3 deployable panels >33.0 dBi gain (max pointing error ±45° Az, ±35° El) Elevation pointing angle: 0.00° Solar Power: 24 solar cells (~24 W BOL LEO)
- #11 When selecting external components for Cubesat, structure and sizing limitation must be put into consideration. Nevertheless, these constraints acted as driving factors in various trade studies in selection components (in particular EPS and Telecom Subsystems). As you can see, the Deployable/Foldable components to fit 6U limitation set by the CubeSat deployment system (CSD). Note: These CSD limitations are current limitations as NASA is currently trying to expand the CSD system to accommodate for 6U Cubesats up to 14kg.
- #12 A simple solar cell sizing was conducted in order to determine what area of solar cells were needed in order to provide power to all critical subsystems, including battery recharging. Through the solar cell sizing, it was determined that a total solar cell area of 0.528 m^2 is required, which corresponds to a total of 192 solar cells (assuming CS solar panel dimensions). Nevertheless, a modular solar panel configuration shown above was selected to provide a total of 192 solar cells. The configuration consists of 6 deployable double-sided solar panels and 2 body mounted solar panels. The deployable 6U panels will have to be custom made by CS and be tested for magazine stacked deployment (24 cells vs 18 cell current configuration). In order to allow for telecommunication during times in eclipse, the battery capacity must be properly sized. Through a battery DoD analysis, it was determined that 2 30Whr batteries will provide adequate power and charge state over the desired 2 year mission lifetime. The K/Ka-Band reflectarray is developed off a 3U turkey tail solar array, which consists of 24 cells. Although the EPS subsystem analysis did not include these additional solar cells, they do provide a redundacy for power generation. FLEX EPS system was selected based off its tested integration with batteries and base solar panles. It also provides numerous voltage inputs for various subsystems. Area of one solar cell (CS): 0.00275 m2
- #13 The overarching, broad pointing requirements for the constellation call for each CubeSat to be continuously pointing towards the Earth during DTE/DFE communication windows (dictates reflectarray and solar array positioning & pointing) and pointing towards the space/ground assets during UHF communication windows. In order to achieve these requirements, a 3-axis stabilized spacecraft is required. Nevertheless, the BCT-XACT module was selected as a preliminary baseline for the ADCS subsystem. It contains the necessary actuators and sensors to achieve 3-axis stabilization with pointing accuracy shown above. To compensate for reaction wheel desaturation, the cold gas thruster will provide desaturation capabilities. Pointing accuracy is 1 sigma confidenc.e for all axes
- #14 The propulsion system was selected based off a preliminary propulsion budget discussed later in the presentation. It is currently being developed by the Georgia Tech Space Systems Design Laboratory and has numerous performance capabilities shown in the table. In particular, it provides a delta-v of 31.5 m/s and a propellant mass of 920 g which is sufficient for initial orbit insertion, station keeping and rxn wheel desaturation. The system is a derivative based off the existing architecture being implemented on Inspire. Lastly, the system contains 7 nozzles for thrusting providing up to 6 DoF control. Chemical propulsion chosen over electrical propulsions due to thrust as well as power requirements
- #15 The flight computer was selected based off the need for an architecture that is robust and reliable. The Proton 200k-L flight computer has flight heritage, powerful, and is robust through rad hardening and redundant flight software architecture.
- #16 Mass budget here provides a preliminary estimate of the total mass of each 6U CubeSat. The mass of each component is provided (based on technical specs sheet) and a contingency factor was added in order to account of things such as custom manufacturing costs, additional weightage due to electrical wiring, harnesses, material selection, etc. For components which a know mass is given but may require further development (e.g. cold gas thruster, IRIS v2 Transponder), a 15% contingency was added. For components which the mass was not fully know and based off an analogous component (e.g. 6U solar panels and heaters), a 20% contingency was added. As you can see, our CubeSat weights around 12.2 kg, which is well below the maximum payload value (MPV) of 14 kg set by the Planetary Deployer. The 13% margin allows for adequate flexibility for future developments.
- #18 Safe Mode: Mode occurs when CubeSat enters eclipse. DTE communication link, EPS system, and flight computer are all on at full power, UHF communications and ADCS are operating at minimal duty cycle, thermal running at half duty cycle. UHF RX/TX Mode: Mode occurs when CubeSat enters the UHF Transmit & Receive portion of operations mode. This mode will occur while the CubeSat is in eclipse and will operate UHF portion of telecom subsystem at full power. Mars Telecom Mode :Mode occurs when CubeSat enters the mars telecom portion of operations mode. telecom, flight computer, EPS System all operates at full power. ADCS operates at half duty cycle power as the CubeSat must be frequently reoriented to face Earth for DTE transmission. Maneuvering Mode: Mode occurs when CubeSat needs to perform a TCM or orbital maitainence maneuver.
- #20 1 Orbit Battery Charge Simulation Assumes orbit-average power generation through daylight period Can see various operation modes in detail Specific Power Draw Orbit-in-a-life duty cycle Surface asset time of 13 minutes (occurs twice in daylight, once in eclipse)
- #27 Cubesat <-> Earth: Worst Case is 2% of Best Case Total Data Throughput Cubesat <-> Surface: Worst Case is 62% of Best Case Total Data Throughput CubeSat <-> Orbiter: Worst Case is 20% of Best Case Total Data Throughput
- #30 Mass/Structure: Optimized configuration meets CSD deployer requirements Telecom: Performed Link Budget to see if DTE/DFE was possible. Ka Band + KaPDA (high gain) allow for communication UHF capability to talk with other assets (mainly Electra Radio compatible) Power: Optimized to meet power requirements of s/c bus (mostly dictated by telecom subsystem in operational mode) Considered shading effects (both body and shadow) due to Ka Antenna primarily Using ephemeris data, found max solar angle and optimized Solar Cell system based off worst case scenario
- #34 CubeSat <-> Earth: Worst Case is 2% of Best Case Total Data Throughput CubeSat <-> Surface: Worst Case is 62% of Best Case Total Data Throughput CubeSat <-> Orbiter: Worst Case is 20% of Best Case Total Data Throughput
- #35 CubeSat <-> Earth: Worst Case is 2% of Best Case Total Data Throughput CubeSat <-> Surface: Worst Case is 62% of Best Case Total Data Throughput CubeSat <-> Orbiter: Worst Case is 20% of Best Case Total Data Throughput
- #36 CubeSat <-> Earth: Worst Case is 2% of Best Case Total Data Throughput CubeSat <-> Surface: Worst Case is 62% of Best Case Total Data Throughput CubeSat <-> Orbiter: Worst Case is 20% of Best Case Total Data Throughput
- #37 CubeSat <-> Earth: Worst Case is 2% of Best Case Total Data Throughput CubeSat <-> Surface: Worst Case is 62% of Best Case Total Data Throughput CubeSat <-> Orbiter: Worst Case is 20% of Best Case Total Data Throughput
- #38 CubeSat <-> Earth: Worst Case is 2% of Best Case Total Data Throughput CubeSat <-> Surface: Worst Case is 62% of Best Case Total Data Throughput CubeSat <-> Orbiter: Worst Case is 20% of Best Case Total Data Throughput
- #39 CubeSat <-> Earth: Worst Case is 2% of Best Case Total Data Throughput CubeSat <-> Surface: Worst Case is 62% of Best Case Total Data Throughput CubeSat <-> Orbiter: Worst Case is 20% of Best Case Total Data Throughput
- #40 Here is a CAD model of the overall cubesat in its deployed configuration with its respective front and back isometric views.
- #43 CubeSat <-> Earth: Worst Case is 2% of Best Case Total Data Throughput CubeSat <-> Surface: Worst Case is 62% of Best Case Total Data Throughput CubeSat <-> Orbiter: Worst Case is 20% of Best Case Total Data Throughput